Forming a non single crystal semiconductor layer by using an electric current

ABSTRACT

A semiconductor device which has a non-single crystal semiconductor layer formed on a substrate and in which the non-single crystal semiconductor layer is composed of a first semiconductor region formed primarily of non-single crystal semiconductor and a second semi-conductor region formed primarily of semi-amorphous semiconductor. The second semiconductor region has a higher degree of conductivity than the first semiconductor region so that a semi-conductor element may be formed.

This is a divisional application of Ser. No. 07/487,904, filed Mar. 5,1990, now abandoned which itself was a divisional of Ser. No. 098,705filed Sep. 18, 1987, now abandoned which was a continuation of Ser. No.775,767 filed Sep. 13, 1985, now abandoned which was a divisional ofSer. No. 278,418 filed Jun. 29, 1981, now U.S. Pat. No. 4,581,620.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a semiconductor device formed usingnon-single crystal semiconductor.

2. Description of the Prior Art

Heretofore, there has been proposed a semiconductor device formed usingsemi-amorphous semiconductor.

The semi-amorphous semiconductor herein mentioned is defined as asemiconductor which is formed of a mixture of a microcrystallinesemiconductor and a non-crystalline semi-conductor and in which themixture doped with a dangling bond neutralizer and the microcrystallinesemiconductor has a lattice strain.

In the semiconductor device using the semi-amorphous semiconductor, thesemi-amorphous semiconductor formed in the shape of a layer provides alarge optical absorption coefficient as compared with a single crystalsemiconductor. Accordingly, with a semi-amorphous semiconductor layer ofsufficiently smaller thickness than the layer-shaped single crystalsemiconductor of the semiconductor device using the single crystalsemiconductor, it is possible to achieve a higher photoelectricconversion efficiency than that obtainable with the single crystalsemiconductor device.

Further, in the semi-camorphous semiconductor device, the semi-amorphoussemiconductor provides a high degree of photoconductivity, a high degreeof dark-conductivity, a high impurity ionization rate and a largediffusion length of minority carriers as compared with an amorphous orpolycrystalline semiconductor. This means that the semi-amorphoussemiconductor device achieves a higher degree of photoelectricconversion efficiency than an amorphous or polycrystalline semiconductordevice.

Accordingly, the semi-amorphous semiconductor device is preferable as asemiconductor photoelectric conversion device.

In the conventional semi-amorphous semiconductor device, however, thenumber of recombination centers contained in the semi-amorphoussemiconductor is as large as about 10¹⁷ to 10¹⁹ /cm³. Owing to such alarge number of recombination centers, the diffusion length of theminority carriers in the semi-amorphous semiconductor is not set to adesirable value of about 1 to 50 μm which is intermediate between 300Åwhich is the diffusion length of the minority carriers in an amorphoussemiconductor and 10³ μm which is the diffusion length of the minoritycarriers in a single crystal semiconductor. Therefore, according to theconventional semiconductor technology, the semi-amorphous semiconductordevice has a photoelectric conversion efficiency as low as only about 2to 4%.

Further, there has been proposed, as the semiconductor device using thesemi-amorphous semiconductor, a semiconductor device which has aplurality of electrically isolated semiconductor elements.

In such a prior art semiconductor device, however, the structure forisolating the plurality of semiconductor elements inevitably occupies anappreciably large area relative to the overall area of the device.Therefore, this semiconductor device is low in integration density. Inaddition, the structure for isolating the plurality of semiconductorelements is inevitably complex. Therefore, the semiconductor device ofthis type cannot be obtained with ease and at low cost.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide a novelsemiconductor device which possesses a higher degree of photoelectricconversion efficiency than does the conventional semiconductor device.

Another object of the present invention is to provide a novelsemiconductor device in which a plurality of electrically isolatedsemiconductor elements are formed with higher integration density.

Yet another object of the present invention is to provide a novelsemiconductor device which is easy to manufacture at low cost.

Other object, features and advantages of the present invention willbecome more apparent from the following description taken in conjunctionwith the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A to 1G schematically show, in section, a sequence of stepsinvolved in the manufacture of a semiconductor device in accordance withan embodiment of the present invention;

FIG. 2 is a schematic diagram illustrating an arrangement for theformation of a non-single crystal semiconductor in the step of FIG. 1C;

FIG. 3 is a graph showing the temperature vs. dark currentcharacteristic of a second semiconductor region in the semiconductordevice of the present invention;

FIG. 4 is a graph showing the spin density of a dangling bond in thesecond semiconductor region in the semiconductor device of the presentinvention;

FIG. 5 is a graph showing that the non-single crystal semiconductorobtained by the manufacturing method of FIG. 1 assumes a stable state asis the case with the single crystal semiconductor and the amorphous one;

FIGS. 6A to 6H are schematic secitonal views showing a sequence of stepsinvolved in the manufacture of a semiconductor in accordance withanother embodiment of the present invention;

FIGS. 7A to 7F are schematic sectional views showing a sequence of stepsinvolved in the manufacture of a semiconductor in accordance withanother embodiment of the present invention;

FIG. 8 is a timing chart explanatory of a method for the formation of asecond semiconductor region in the step of FIG. 7E; and

FIG. 9 is a timing chart explanatory of an example of the use of thesemiconductor device produced by the manufacturing method depicted inFIGS. 7A to 7F.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

An example of the semiconductor device of the present invention will bedescribed in connection with an example of the manufacturing methodthereof.

FIGS. 1A to 1F illustrate a sequence of steps involved in themanufacture of a semiconductor device in accordance with a embodiment ofthe present invention.

The manufacture starts with the preparation of a substrate 2 having aflat major surface 1, such as shown in FIG. 1A. In this embodiment, thesubstrate 2 is made of a light-permeable insulator such as glass.

The next step consists in the formation of a plurality of conductivelayers 3 on the major surface 1 of the substrate 2 by a known method, asdepicted in FIG. 1B. The conductive layers 3 are made of metal in thisexample and light-permeable and has a desired pattern on the majorsurface 1 of the substrate 2. In this example each of the conductivelayers 3 extends at both ends to conductive layers 4 and 5,respectively, which are formed on the major surface 1 of the substrate 2in advance.

Next, an insulating layer 6 of silicon nitride, for example, is formedas by the plasma CVD method on the conductive layer 3. The insulatinglayer 6 has a thickness of, for example, 5 to 50 Å, preferably 10 to 25Å, small enough to permit the passage therethrough of a tunnel current,and this layer 6 is light-permeable, too.

Then, a non-single crystal semiconductor 7 doped with a dangling bondneutralizer is formed in layer on the major surface 1 of the substrate 2to cover each of the conductive layers 3 through the insulating layer 6,as depicted in FIG. 1C. In this example the non-single crystalsemiconductor layer extends on the outer side surfaces of the conductivelayers 3 and 5. The layer 7 can be formed 0.5 to 5 μm thick.

The non-single crystal semiconductor layer 7 can be formed of non-singlecrystal silicon, germanium or additional semiconductor material compoundexpressed by Si₃ N_(4-x) (0<x<4), SiO_(2x) (0<x<2), SiC_(x) (0<x<1) orSi_(x) Ge_(1-x) (0<x<1). The dangling bond neutralizer is composed ofhydrogen or halogen such as fluoride or chlorine.

The non-single crystal semiconductor 7 means a semi-amorphoussemiconductor, an amorphous semiconductor or a mixture thereof and it isdesired to be the semi-amorphous semiconductor. The semi-amorphoussemiconductor is formed of a mixture of a microcrystalline semiconductorand a non-crystalline semiconductor and the mixture is doped with adangling bond neutralizer and the microcrystalline semiconductor has alattice strain. According to an embodiment of the semi-amorphoussemiconductor, the microcrystalline semiconductor and thenon-crystalline semiconductor are both, for example, silicon; in thiscase, the mixture is normally silicon and the microcrystallinesemiconductor is dispersed in the non-crystalline semiconductor. In thecase where the non-single crystal semiconductor 7 is the abovesaidsemi-amorphous semiconductor, it can be formed by the method describedhereinbelow.

FIG. 2 illustrates an embodiment of the non-single crystallinesemiconductor manufacturing method of the present invention and anarrangement therefor, in which a reaction chamber 31 is employed.

The reaction chamber 31 has a gas inlet 32, a gas ionizing region 33,semiconductor depositing region 34, and a gas outlet 25 which areprovided in this order. The gas ionizing region 33 has a smallereffective cross-section than the semiconductor depositing region 34.Arranged around the gas ionizing region 33 is an ionizing high-frequencypower source 36 which applies to the gas ionizing region 33 an ionizinghigh-frequency electromagnetic field of, for example, as 1 to 10 GHz,preferably 2.46 GHz. The high-frequency power source 36 may be formed bya coil which is supplied with a high-frequency current.

Disposed around the semiconductor depositing region 34 of the reactionchamber 31 is an orientating-accelerating high-frequency power source 39which applies to the semiconductor depositing region 34 anorientating-accelerating electric field perpendicularly to the surfacesof the substrates 2. The electric field has a relatively low alternatingfrequency, for example, 1 to 100 MHz, preferably 13.6 MHz. Thehigh-frequency power source 39 may be formed by a coil which is suppliedwith a high-frequency current. The high-frequency power source 39 iscovered with a heating source 40 which heats the semiconductordepositing region 34 and consequently the substrates 2. The heatingsource 40 may be a heater which is supplied with a direct current.

To the gas inlet 32 of the reaction chamber 31 is connected one end of amixture gas supply pipe 41, to which are connected a main semiconductormaterial compound gas source 47, impurity compound gas sources 48 and49, an additional semiconductor material compound gas source 50 and acarrier gas source 51 through control valves 42, 43, 44, 45, and 46,respectively.

From the main semiconductor material compound gas source 47 is supplieda main semiconductor material compound gas A such as a mainsemiconductor material hydride gas, a main semiconductor material halidegas, a main semiconductor material organic compound gas or the like. Themain semiconductor material gas A is, for example, a silane (SiH₄) gas,a dichlorosilane (SiH₂ Cl₂) gas, a trichlorosilane (SiHCl₃) gas, silicontetrachloride (SiCl₄) gas, a silicon tetrafluoride (SiF₄) gas or thelike. From the impurity compound gas source 48 is supplied an impuritycompound gas B such as hydride, halide or hydroxide gas of a metallicimpurity, for example, a trivalent impurity such as Ga or In, or aquadrivalent impurity such as Sn or Sb. From the impurity compound gassource 49 is supplied an impurity compound gas C such as hydride, halideor hydroxide gas of a metallic impurity, for example, a pentavalentimpurity such as As or Sb. From the additional semiconductor materialcompound gas source 50 is supplied an additional semiconductor materialcompound gas D such as an additional semiconductor material hydroxide orhalide gas of nitrogen, germanium, carbon, tin, lead or the like, forexample, an SnCl₂, SnCl₄, Sn(OH)₂, Sn(OH)₄, GeCl₄, CCl₄, NCl₃, PbCl₂,PbCl₄, Pb(OH)₂, Pb(OH)₄ or the like gas. From the carrier gas source 51is supplied a carrier gas E which is a gas composed of or contains aHelium (He) and/or neon (Ne) gas, for example, a gas composed of thehelium gas, a neon gas or a mixer gas of the helium gas or the neon gasand a hydrogen gas.

To the gas outlet 25 of the reaction chamber 31 is connected one end ofa gas outlet pipe 52, which is connected at the other end to anexhauster 54 through a control valve 53. The exhaust 54 may be a vacuumpump which evacuate the gas in the reaction chamber 1 through thecontrol valve 53 and the gas outlet tube 52.

It is preferred that a gas homegenizer 55 is provided midway between thegas ionizing region 33 and the semiconductor depositing region 34 in thereaction chamber 31.

In the semiconductor depositing region 34 of the reaction chamber 31there is placed on a boat 38 as of quartz the substrate 2 which hasprovided on the major surface thereof the conductive layer 3 and theinsulating layer 6 thereon, as described previously in respect of FIG.1C.

As described above, the substrate 2 is placed in the semiconductordepositing region 34 of the reaction chamber 31 and, in the state inwhich the gas in the reaction chamber 31 is exhausted by the exhauster54 through the gas outlet 25, the gas outlet pipe 52 and the controlvalve 53, a mixture gas F containing at least the main semiconductormaterial compound gas A available from the main semiconductor materialcompound gas source 47 via the control valve 42 and the carrier gas Eavailable from the carrier gas source 51 via the control valve 46 isintroduced into the gas ionizing region of the reaction chamber 31 viathe gas inlet 32. In this case, the mixture gas F may contain theimpurity compound gas B available from the impurity compound gas source48 via the control valve 43 or the impurity compound gas C availablefrom the impurity compound gas source 49 via the control valve 44.Further, the mixture gas F may also contain the additional semiconductormaterial compound gas available from the additional semiconductormaterial compound gas source 50 via the control valve 45. The amount ofthe carrier gas E contained in the mixture gas F may be 5 to 99 flowrate %, in particular, 40 to 90 flow rate % relative to the mixture gasF.

A high-frequency electromagnetic field is applied by the ionizing,high-frequency power source 36 to the mixture gas F introduced into thegas ionizing region 33, by which the mixture gas F is ionized into aplasma, thus forming a mixture gas plasma G in the gas ionizing region33. In this case, the high-frequency electromagnetic field may be onethat has a 10 to 300 W high-frequency energy having a frequency of 1 to100 GHz, for example, 2.46 GHz.

Since the electromagnetic field employed for ionizing the mixture gas Finto the mixture gas plasma G in the gas ionizing region 33 is amicro-wave electromagnetic field and has such a high frequency asmentioned above, the ratio of ionizing the mixture gas F into themixture gas plasma G is high. The mixture gas plasma G contain at leasta carrier gas plasma into which the carrier gas contained in the mixturegas F is ionized and a main semiconductor material compound gas plasmainto which the semiconductor compound gas is ionized. Since the carriergas contained in the mixture gas F is a gas composed of or containingthe helium gas and/or the neon gas, it has a high ionizing energy. Forexample, the helium gas has an ionizing energy of 24.57 eV and the neongas an ionizing energy of 21.59 eV. In contrast thereto, hydrogen andargon employed as the carrier gas in the conventional method have anionizing energy of only 10 to 15 eV. Consequently, the carrier gasplasma contained in the mixture gas plasma has a large energy.Therefore, the carrier gas plasma promotes the ionization of thesemiconductor material compound gas contained in the mixture gas F.Accordingly, the ratio of ionizing the semiconductor material compoundgas contained in the fixture gas into the semiconductor materialcompound gas plasma is high.

Consequently, the flow rate of the semiconductor material compound gasplasma contained in the mixture gas plasma G formed in the gas ionizingregion 33 is high relative to the flow rate of the entire gas in the gasionizing region 33.

The same is true of the case where the additional semiconductor materialcompound gas D, the metallic impurity compound gas B or C is containedin the mixture gas F and ionized into its gas plasma.

The mixture gas plasma G thus formed is flowed into the semiconductordepositing region 34 through the gas homogenizer 55 by exhausting thegas in the reaction chamber 31 by means of the exhauster 54 through thegas outlet 25, the gas outlet pipe 52 and the control valve 53.

By flowing the mixture gas plasma G into the semiconductor depositingregion 34, semiconductor material is deposited on the substrate 2 placedin the semiconductor depositing region 34. In this case, the flow rateof the mixture gas F introduced into the reaction chamber 31, especiallythe flow rate of the carrier gas E contained in the mixture gas F iscontrolled beforehand by the adjustment of the control valve 46 and theflow rate of the gas exhausted from the reaction chamber 31 through thegas outlet 25 is controlled in advance by adjustment of the controlvalve 53, by which the atmospheric pressure in the reaction chamber 31is held below 1 atm. Moreover, the substrate 2 is maintained at arelatively low temperature under a temperature at which semiconductorlayers deposited on the substrate 2 become crystallized, for example, inthe range from the room temperature to 700° C. In the case ofmaintaining the substrate 2 at room temperature, the heating source 40need not be used, but in the case of holding the substrate 2 at atemperature higher than the room temperature, the heating source 40 isused to heat the substrate 2. Furthermore, the deposition of thesemiconductor material on the substrate 2 is promoted by theorientating-accelerating electric field established by theorientating-accelerating high-frequency source 39 in a directionperpendicular to the surfaces of the substrate 2.

As described above, by depositing the semiconductor material on thesubstrate 2 in the semiconductor depositing region 34 in the state inwhich the atmospheric pressure in the reaction chamber 31 is held lowand the substrate 2 is held at a relatively low temperature, a desirednon-single crystal semiconductor 7 which is formed of a mixture of amicrocrystalline semiconductor and a non-crystalline semiconductor andin which the mixture is doped with a dangling bond neutralizer is formedon the substrate 2.

In this case, the mixture gas plasma in the semiconductor depositingregion 34 is the mixture plasma having flowed thereinto from the gasionizing region 33, and hence is substantially homogeneous in thesemiconductor depositing region 34. Consequently, the mixture gas plasmais substantially homogeneous over the entire surface of the substrate 2.

Accordingly, it is possible to obtain on the substrate 2 the non-singlecrystal semiconductor 7 which is homogeneous in the direction of itssurface and has substantially no or a neglibibly small number of voids.

In addition, since the flow rate of the semiconductor material compoundgas plasma contained in the mixture gas plasma G formed in the gasionizing region 33 is large with respect to the flow rate of the entiregas in the gas ionizing region 33, as mentioned previously, the flowrate of the semiconductor material compound gas plasma contained in themixture gas on the surface of the substrate 2 in the semiconductordepositing region 34 is also large relative to the flow rate of theentire gas on the surface of the substrate 2. This ensures that thenon-single crystal semiconductor 7 deposited on the surface of thesubstrate 2 has substantially no or a neglibibly small number of voidsand is homogeneous in the direction of the surface of the substrate 2.

Besides, since the carrier gas plasma contained in the mixture gasplasma formed in the gas ionizing region 33 has a large ionizing energy,as referred to previously, the energy of the carrier gas plasma has alarge value when and after the mixture gas plasma flows into thesemi-conductor depositing region 34, and consequently the energy of thesemiconductor material compound gas plasma contained in the mixtureplasma on the substrate 2 in the semiconductor depositing region 34 hasa large value. Accordingly, the non-single crystal semiconductor 7 canbe deposited on the substrate 2 with high density.

Furthermore, the carrier gas plasma contained in the mixture gas plasmais composed of or includes the helium gas plasma and/or the neon gasplasma, and hence has a high thermal conductivity. Incidentally, thehelium gas plasma has a thermal conductivity of 0.123 Kcal/mHg°C. andthe neon gas plasma 0.0398 Kcal/mHg°C. Accordingly, the carrier gasplasma greatly contributes to the provision of a uniform temperaturedistribution over the entire surface of the substrate 2. In consequence,the non-single crystal semiconductor 7 deposited on the substrate 2 canbe made homogeneous in the direction of its surface.

Moreover, since the carrier gas plasma contained in the mixture gas inthe semiconductor depositing region 34 is a gas plasma composed of orcontaining the helium gas plasma and/or the neon gas plasma, the heliumgas plasma is free to move in the non-single crystal semiconductor 7formed on the substrate 2. This reduces the density of recombinationcenters which tends to be formed in the non-single crystal semiconductor7, ensuring to enhance its property.

The above has clarified an example of the method for the formation ofthe non-single crystal semiconductor 7 in the case where it is thesemi-amorphous semiconductor. With the above-described method, thenon-single crystal semiconductor 7 can be formed containing a danglingbond neutralizer in an amount of less than 5 mol % relative to thesemiconductor 7. Further, the non-single crystal semiconductor 7 can beformed by a microcrystalline semiconductor of a particle size rangingfrom 5 to 200 Å and and equipped with an appropriate lattice strain.

The above has clarified the manufacturing method of the presentinvention and its advantages in the case where the non-single crystalsemiconductor 7 is the semi-amorphous semiconductor. Also in the casewhere the non-single crystal semiconductor 7 is an amorphoussemiconductor or a mixture of the semi-amorphous semiconductor and theamorphous semiconductor, it can be formed by the above-described method,although no description will be repeated.

After the formation of the non-single crystal semiconductor 7 on thesubstrate 2, the insulating layer 8 as of silicon nitride is formed, forexample, by the plasma CVD method on the non-single crystalsemiconductor 7, as depicted in FIG. 1A. The insulating layer 8 is thinenough to permit the passage therethrough of a tunnel current andlight-permeable, as is the case with the insulating layer 6.

Following this, a conductive layer 9 is formed by a known method on thenon-single crystal semiconductor 7 in an opposing relation to theconductive layer 3 through the insulating layer 8 as depicted in FIG.1D. The conductive layer 9 can be provided in the form of a film ofalminum, magnesium or the like. In this example, each conductive layer 9extends across the side of the non-single crystal semiconductor layer 7and the surface 1 of the substrate 2 to the conductive layer 5contiguous to the adjoining conductive layer 9.

Thereafter, a protective layer 10 as of epoxy resin is formed on thesurface 1 of the substrate 2 to extend over the conductive layers 3, 4,5 and 9, the insulating layers 6 and 8 and the non-single crystalsemiconductor layer 7, as shown in FIG. 1E.

Then, a power source 11 is connected at one end with alternate ones ofthe conductive layers 4 and at the other end with intermediate ones ofthem; accordingly, the power source 11 is connected across theconductive layers 3 and 9. At this time, the region Z2 of the non-singlecrystal semiconductor layer 7, except the outer peripheral region Z1thereof, is exposed to high L from the side of the light-permeablesubstrate 2 through the light-permeable conductive layer 3 andinsulating layer 6 by the application of light L, electron-hole pairsare created in the non-single crystal semiconductor 7 to increase itsconductivity. Accordingly, the irradiation by light L during theapplication of the current I to the non-single crystal semiconductor 7facilitates a sufficient supply of the current I to the region Z2 evenif the non-single crystal semiconductor 7 has a low degree ofconductivity or conductivity close to intrinsic conductivity. For theirradiation of the non-single crystal semiconductor 7, a xeron lamp,fluorescent lamp and sunlight, can be employed. According to anexperiment, good results were obtained by the employment of a 10³ -luxxenon lamp. In the region Z2 a semi-amorphous semiconductor S2 isformed, as depicted in FIG. 1G. The mechanism by which thesemi-amorphous semiconductor S2 is formed in the region Z2 is that heatis generated by the current I in the region Z2, by which it is changedin terms of structure.

In the case where the non-single crystal semiconductor 7 is formed ofthe semi-amorphous semiconductor (which will hereinafter be referred toas a starting semi-amorphous semiconductor), the region Z2 istransformed by the heat generated by the current I into thesemi-amorphous semiconductor S2 which contains the microcrystallinesemiconductor more richly than does the starting semi-amorphoussemiconductor. Even if the non-single crystal semiconductor 7 is theamorphous semiconductor or the mixture of the semi-amorphous and theamorphous semiconductor, the semi-amorphous semiconductor S2 is formedto have the same construction as in the case where the non-singlecrystal semiconductor 7 is the semi-amorphous one.

By the thermal energy which is yielded in the region Z2 when thesemi-amorphous semiconductor S2 is formed in the region Z2, danglingbonds of the semiconductor are combined, neutralizing the dangling bondsin that region. The non-single crystal semiconductor 7 is doped with adangling bond neutralizer such as hydrogen and/or halogen. Accordingly,the dangling bond neutralizer is activated by the abovesaid thermalenergy in the region Z2 and its vicinity and combined with the danglingbonds of the semiconductor. As a result of this, the semi-amorphoussemiconductor S2 formed in the region Z2 has a far smaller number ofrecombination centers than the non-single crystal semiconductor.According to our experience, the number of recombination centers in thesemi-amorphous semiconductor S2 was extremely small-on the order of1/10² to 1/10⁴ that of the non-single crystal semiconductor 7.

Since the number of recombination centers in the semi-amorphoussemiconductor S2 is markedly small as described above, the diffusionlength of minority carriers lies in the desirable range of 1 to 50 m.

The thermal energy which is produced in the region Z2 during theformation therein of the semi-amorphous semiconductor S2 contributes tothe reduction of the number of recombination centers and the provisionof the suitable diffusion length of minority carriers. Further, it hasbeen found that the generation of the abovesaid heat contributes to theformation of the semi-amorphous semiconductor S2 with an interatomicdistance close to that of the single crystal semiconductor although thesemiconductor S2 does not have the atomic orientation of the latter. Inthe case where the non-single crystal semiconductor 7 was non-singlecrystal silicon, the semi-amorphous semiconductor S2 was formed with aninteratomic distance of 2.34 Å±20% nearly equal to that 2.34 Å of singlecrystal silicon. Accordingly, the semi-amorphous semiconductor S2 hasstable properties as semiconductor, compared with the non-single crystalsemiconductor 7.

Further, it has been found that the abovementioned heat generationcontributes to the formation of the semi-amorphous semiconductor S2which exhibits an excellent electrical conductivity characteristic. FIG.3 shows this electrical conductivity characteristic, the abscissarepresenting temperature 100/T (°K.⁻¹) and the ordinate dark current logσ (σ:σ cm⁻¹). According to our experiments, in which when the non-singlecrystal semiconductor 7 had a characteristic indicated by the curve al,the currents having densities of 3×10¹ and 1×10³ A/cm² were each appliedas the aforesaid current I for 0.5 sec. while irradiating by the light Lat an illumination of 10⁴ LX, such characteristics as indicated by thecurves a2 and a3 were obtained, respectively. In the case where when thenon-single crystal semi-conductor 7 had such a characteristic asindicated by the curve b1, the currents of the same values as mentionedabove were each applied as the current I for the same period of timeunder the same illumination condition, a characteristics indicated bythe curves b2 and b3 were obtained, respectively. The curve b1 shows thecharacteristic of a non-single crystal semiconductor obtained by adding1.2 mol % of the aforementioned metallic impurity, such as Ga or In, Snor Pb, or As or Sb, to the non-single crystal semiconductor 7 of thecharacteristic indicated by the curve al. As is evident from acomparison of the curves a2, a3 and b2, b3, a semi-amorphoussemiconductor obtained by adding the abovesaid metallic impurity to thesemi-amorphous semiconductor S2 exhibits an excellent conductivitycharacteristic over the latter with such a metallic impurity added. Itis preferred that the amount of metallic impurity added to thesemi-amorphous semiconductor S2 be 0.1 to 10 mol %.

Also it has been found that the aforesaid heat generation greatlycontributes to the reduction of dangling bonds in the semi-amorphoussemiconductor S2. FIG. 4 shows the reduction of the dangling bonds, theabscissa representing the density D (A/cm²) of the current I applied tothe region Z2 when forming the semi-amorphous semiconductor S2 and theordinate representing the normalized spin density G of the danglingbonds. The curves C1, C2 and C3 indicate the reduction of dangling bondsin the cases where the current I was applied to the region Z2 for 0.1,0.5 and 2.5 sec., respectively. It is assumed that such reduction of thedangling bonds is caused mainly by the combination of semiconductors asthe semi-amorphous semiconductor S2 contains as small an amount ofhydrogen as 0.1 to 5 mol % although the non-single crystal semiconductor7 contains as large an amount of hydrogen as 20 mol % or so.

And the semi-amorphous semiconductor S2 assumes stable states ascompared with the single crystal semiconductor and the amorphoussemiconductor, as shown in FIG. 5 which shows the relationship betweenthe configurational coordinate φ on the abscissa and the free energy Fon the ordinate.

FIG. 1 illustrates a semiconductor device according to the presentinvention produced by the manufacturing method described in theforegoing. On the substrate 2 there are provided the semi-amorphoussemiconductor region S2 of the abovesaid excellent properties and thenon-single crystal semiconductor region S1 formed by that region Z1 ofthe non-single crystal semiconductor layer 7 in which the current I didnot flow during the formation of the semi-amorphous semiconductor regionS2. The non-single crystal region S1 does not possess the abovesaidexcellent properties of the semi-amorphous semiconductor region S2.Especially, the region S1 does not have the excellent conductivitycharacteristic of the region S2 and the former can be regarded as aninsulating region relative to the latter. Consequently, the non-singlecrystal semiconductor region S1 electrically isolates the semi-amorphoussemiconductor regions S2 from adjacent ones of them. The conductivelayer 3, the insulating layer 6 and the semi-amorphous semiconductorregion S2 make up one MIS structure, and the conductive layer 9, theinsulating layer 8 and the semi-amorphous semiconductor region S2 makeup another MIS structure. Such a construction is similar to that of aMIS type photoelectric conversion semiconductor device proposed in thepast. Accordingly, by using the conductive layers 3 and 9 as electrodesand applying light to the semiconductor device of FIG. 1F from theoutside thereof so that the light may enter the semi-amorphoussemiconductor S2 through the light-permeable subtrate 2, conductivelayer 3 and insulating layer 6, it is possible to obtain thephotoelectric conversion function similar to that obtainable with theconventional MIS type photoelectric conversion semiconductor device. Inthe semi-amorphous semiconductor S2 of the semi-amorphous semiconductordevice of FIG. 1F, however, the number of recombination centers is farsmaller than in the case of an ordinary semi-amorphous semiconductor(corresponding to the case where the non-single crystal semiconductor 7prior to the formation of the semi-amorphous semiconductor S2 issemi-amorphous); the diffusion length of minority carriers is in therange of 1 to 50 μm; and the interatomic distance is close to that inthe single crystal semiconductor. Therefore, the semi-conductor deviceof FIG. 1G has such an excellent feature that it exhibits a markedlyhigh photoelectric conversion efficiency of 8 to 12%, as compared withthat of the prior art semiconductor device (corresponding to a devicewhich has the construction of FIG. 1E and has its non-single crystalsemiconductor 7 formed of semi-amorphous semiconductor).

Next, a description will be given, with reference to FIGS. 6A to 6H, ofa second embodiment of the semiconductor device of the presentinvention, together with its manufacturing method.

The manufacture starts with the preparation of an insulating substrate62 with a major surface 61, such as shown in FIG. 6A. The substrate 61is one that has an amorphous material surface, such as a glass plate,ceramic plate or silicon wafer covered over the entire area of itssurface with a silicon oxide film.

Then as shown in FIG. 6B, a non-single crystal semiconductor layer 63 isformed to a thickness of 0.3 to 1 μm on the substrate 62 by the methoddescribed previously in respect of FIG. 2 in the same manner as thenon-single crystal semiconductor layer 7 described previously withrespect of FIG. 1C.

Following this, as shown in FIG. 6C, a ring-shaped insulating layer 64of semiconductor oxide is formed by known oxidizing method to arelatively large thickness of, for example, 0.2 to 0.5 μm on the side ofthe surface of the layer 63. Then, an insulating layer 65 of amorphoussemiconductor nitride is formed relatively thin, for example, 50 to 100Å in that region of the layer 63 surrounded by the insulating layer 64.

Thereafter, as depicted in FIG. 6D, a conductive layer 66 of amorphousor semi-amorphous semiconductor is formed on the insulating layer 65 toextend across the ring-shaped insulating layer 64 diametrically thereof(in the direction perpendicular to the sheet in the drawing). Thesemiconductor layer 66 is doped with 0.1 to 5 mol % of an N typeconductive material such as Sb or As, or a P type conductive materialsuch as In or Ga. Further, windows 67 and 68 are formed in theinsulating layer 65 on both sides of the conductive layer 66 where thewindows are contiguous to the insulating layer 64. A conductive layers69 and 70 similar to the layer 66 extending on the insulating layer 64are formed to make ohmic contact with the semiconductor layer 63 throughthe windows 67 and 68, respectively.

Next, by ion implantation of an impurity into those two regions of thesemiconductor layer 63 which are surrounded by the ring-shapedinsulating layer 64 and lie on both sides of the conductive layer 66, asviewed from above, impurity injected regions 71 and 72 are formed, asdepicted in FIG. 6E. In this case, it must be noted here that theregions 71 and 72 are surrounded by those non-impurity-injected regions73 and 74 of the layer 63 underlying the insulating layer 64 and theconductive layer 66, respectively.

After this, an inter-layer insulating layer 75 is formed to extend onthe insulating layers 64 and 65 and the conductive layers 66, 69 and 70,as illustrated in FIG. 6F.

This is followed by connecting a power source 76 across the conductivelayers 69 and 70, by which the current I flows through the regions 71,72 and 74. In this case, no current flows in the region 73. By thecurrent application, heat is generated in the regions 71, 72 and 74. Inconsequence, as described previously in respect of FIGS. 1F and 1G, theregions 71, 72 and 74 respectively undergo a structural change intosemi-amorphous semiconductor regions 77, 78 and 79, respectively, asshown in FIG. 6H.

In this way, the semiconductor device of the second embodiment of thepresent invention is obtained.

In the semiconductor device of the present invention shown in FIG. 6H,the regions 77, 78 and 79 correspond to the semi-amorphous semiconductorregion S2 in FIG. 1G, providing excellent properties as a semiconductordevice. The region 73 corresponds to the non-single crystalsemiconductor S1 in FIG. 1G, and hence it has the property of aninsulator. The regions 77, 78 and 79 are encompassed by the region 73,so that the regions 77 to 79 are essentially isolated from the otheradjoining regions 77 to 79 electrically.

The semiconductor device illustrated in FIG. 6H has a MIS type fieldeffect transition structure which employs the regions 77 and 78 on theinsulating substrate 62 as a source and a drain region, respectively,the region 79 as a channel region, the insulating layer 65 as a gateinsulating layer, the conductive layer 66 as a gate electrode and theconductive layers 69 and 70 as a source and a drain electrode,respectively. Since the regions 77, 78 and 79 serving as the source, thedrain and the channel region have excellent properties as asemiconductor, the mechanism of an excellent MIS type field effecttransistor can be obtained. In this example, an excellent transistormechanism can ben obtained even if the conductivity type of the region79 is selected opposite to those of the regions 77 and 78.

Next, a description will be given, with reference to FIGS. 7A to 7E, ofa third embodiment of the present invention in the order of stepsinvolved in its manufacture.

The manufacture begins with the preparation of such an insulatingsubstrate 82 as shown in FIG. 7A which has a flat major surface 81.

The next step consists in the formation of a conductive layer 83 on thesubstrate 82 as shown in FIG. 7B.

This is followed by forming, as depicted in FIG. 7C, a non-singlecrystal semiconductor layer 84, for example, 0.5 to 1 μm thick on theconductive layer 83 in the same manner as non-single crystalsemiconductor 7 in FIG. 1C.

After this, another conductive layer 85 is formed on the non-singlecrystal layer 84 as depicted in FIG. 7D.

Thereafter, the non-single crystal semiconductor layer 84 is exposed toirradiation by laser light, with a power source 86 connected across theconductive layers 83 and 85, as illustrated in FIG. 7E. In this case, alaser beam L' having a diameter of 0.3 to 3 μm, for instance, is appliedto the non-single crystal semiconductor layer 84 at selected ones ofsuccessive positions a₁, a₂, . . . thereon, for example, a₁, a₃, a₄, a₈,a₉, at the moments t₁, t₃, t₄, t₈, t₉, . . . in a sequential order, asdepicted in FIG. 8. By this irradiation the conductivity of thenon-single crystal semiconductor layer 84 is increased at the positionsa₁, a₃, a₄, a₈, a₉, . . . to flow there currents I₁, I₃, I₄, I₈, I₉, . .. , thus generating heat. As a result of this, the non-single crystalsemiconductor layer 84 undergoes a structural change at the positionsa₁, a₃, a₄, a₈, a₉, . . . to provide semi-amorphous semiconductorregions K₁, K₃, K₄, K₈, K₉, . . . , as showin in FIG. 7F.

In this way, the semiconductor device of the third embodiment of thepresent invention is obtained.

In the semiconductor device of the present invention illustrated in FIG.7F, the regions K₁, K₃, K₄, K₈, K₉, . . . correspond to thesemi-amorphous semiconductor region S2 in FIG. 1G, providing a highdegree of conductivity. Regions K₂, K₅, K₆, K₇, K₁₁, . . . at thepositions a₂, a₅, a₆, a₇, a₁₁, . . . other than the regions K₁, K₃, K₄,K₈, K₉, . . . correspond to the non-single crystal semiconductor S1 inFIG. 1G, providing the property of an insulator.

The semiconductor device shown in FIG. 7F can be regarded as a memory inwhich "1", "0", "1", "1", "0", . . . in the binary representation arestored at the positions a₁, a₂, a₃, a₄, a₅, . . . , respectively. Whenthe regions K₁, K₃, K₄, . . . and consequently the positions a₁, a₃, a₄,. . . are irradiated by a laser beam of lower intensity than theaforesaid one L' while at the same time connecting the power sourceacross the conductive layers 83 and 85 via a load, the regions K₁, K₃,K₄, . . . become more conductive to apply a high current to the load.Even if the regions K₂, K₅, K₆, . . . are irradiated by suchlow-intensity laser beam, however, no current flows in the load, or ifany current flows therein, it is very small. Accordingly, by irradiatingthe positions a₁, a₂, a₃, . . . by low-intensity light successively atthe moments t₁, t₂, t₃, . . . , outputs corresponding to "1", "0", "1","1", . . . are sequentially obtained in the load, as shown in FIG. 9. Inother words, the semiconductor device of this embodiment has thefunction of a read only memory.

Although in the foregoing embodiments the semiconductor device of thepresent invention has been described as being applied to a photoelectricconversion element, a MIS type field effect transistor and a photomemory, the embodiments should not be construed as limiting theinvention specifically thereto. According to this invention, it ispossible to obtain a photoelectric conversion element array composed ofa plurality of series-connected photoelectric conversion elements asshown in FIG. 1G. Further, it is possible to form an inverter by aseries connection of two MIS type field effect transistors as depictedin FIG. 6H. In this case, those regions of either of MIS type fieldeffect transistors which serve as the source and drain regions thereofdiffer in conductivity type from those of the other and the region whichserves as the channel region is doped, as required, with an impuritythat makes it opposite in conductivity type to that of the source anddrain regions. Moreover, the semi-amorphous semiconductor forming thesemiconductor device according to the present invention permits directtransition of electrons even at lower temperatures than does theamorphous semiconductor. Therefore, it is also possible to obtainvarious semiconductor elements that are preferred to utilize the directtransition of electrons. Also it is possible to obtain varioussemiconductor elements, including a bipolar transistor and a diode, ofcourse, which have at least one of PI, PIN, PI and NI junctions in thesemi-amorphous semiconductor layer forming the semiconductor deviceaccording to the present invention.

It will be apparent that many modifications and variations may beeffected without departing from the scope of the novel concepts of thepresent invention.

What is claimed is:
 1. A method of forming a semiconductor layercomprising the steps of:forming a semiconductor layer on a substrate;and applying an electric current to at least a portion of saidsemiconductor layer to modify said portion of the semiconductor layer tobe a semi-amorphous semiconductor where said semi-amorphoussemiconductor is a mixture of a non-crystalline structure and amicrocrystalline structure of the semiconductor and has a lattice strainand said semi-amorphous semiconductor is doped with a dangling bondneutralizer comprising hydrogen or fluorine at less tha 5 mol %.
 2. Amethod according to claim 1 wherein said semiconductor layer issubstantially an intrinsic conductivity type.
 3. A method according toclaim 1 wherein the carrier length range of at least the minoritycarriers in the semi-amorphous semiconductor is at least one micron. 4.A method according to claim 1 wherein said substrate has an insulatingsurface.
 5. A method according to claim 1 wherein said semiconductorcomprises a material selected from the group consisting of Si, Ge, Si₃N_(4-x) (0<x<4), SiO_(2-x) (0<x<2), SiC_(x) (0<x<1), or Si_(x) Ge_(1-x)(0<x<1).
 6. A method according to claim 1 wherein said non-singlecrystal semiconductor layer is formed by glow dischage CVD method.
 7. Amethod according to claim 1 wherein said semi-amorphous semiconductorlayer is an active layer of insulated gate field effect transistor. 8.In a method of manufacturing a field effect transistor comprisingsource, drain and channel regions, the improvement comprising:forming asemiconductor layer; applying an electric current to said semiconductorlayer to modify said layer to a semi-amorphous semiconductor layer,thereby forming at least said channel region.
 9. A method according toclaim 8 wherein said semi-amorphous semiconductor is a mixture of anon-crystalline structure and a microcrystalline structure of thesemiconductor and has a lattice strain, and said semi-amorphoussemiconductor is doped with a dangling bond neutralizer comprisinghydrogen or fluorine at less than 5 mol %.
 10. A method according toclaim 9 wherein said semiconductor comprises a material selected fromthe group consisting of Si, Ge, Si₃ N_(4-x) (0<x<4), SiO_(2-x) (0<x<2),SiC_(x) (0<x<1), or Si_(x) Ge_(1-x) (0<x<1).
 11. A method ofmanufacturing a field effect transistor comprising the stepsof:manufacturing a field effect transistor comprising at least source,drain and channel semiconductor layers, a gate electrode adjacent tosaid channel semiconductor layer with an insulating layer therebetween,source and drain electrodes connected to said source and drain regions,respectively; and applying an electric current to at least to saidchannel semiconductor layer in order to modify said layer to asemi-amorphous semiconductor layer.
 12. A method according to claim 11wherein said semi-amorphous semiconductor is a mixture of anon-crystalline structure and a microcrystalline structure of thesemiconductor and has a lattice strain and said semi-amorphoussemiconductor is doped with a dangling bond neutralizer comprisinghydrogen or fluorine at less than 5 mol %.
 13. A method according toclaim 11 wherein said semiconductor comprises a material selected fromthe group consisting of Si, Ge, Si₃ N_(4-x) (0<x<4), SiO_(2-x) (0<x<2),SiC_(x) (0<x<1), or Si_(x) Ge_(1-x) (0<x<1).
 14. A method according toclaim 11 wherein said electric current is externally applied to saidchannel semiconductor layer through said source and drain electrodes.